The present invention relates to a structure to be adapted in an imaging device for preventing an irregular rotation of a photoconductive drum.
Conventionally, an imaging device is known, such as copy machine, a laser beam printer and the like, making use of a so-called electrophotographic image forming method. In the electrophotographic imaging device, a uniformly charged surface of a photoconductive drum is exposed to light to form a latent image, charged toner is adhered to the latent image to form a toner image, and the toner image is transferred onto a recording sheet and fixed thereon.
In a laser beam printer, for example, a toner cleaner, a discharging unit, a charging unit, a scanning optical system (i.e., scanning/exposing mechanism) for introducing a laser beam onto a photoconductive drum, a developing unit, and a transfer unit disposed around a photoconductive drum, which is rotated at a predetermined peripheral speed, along the rotary direction thereof. An image is transferred at the transfer unit onto a recording sheet, which is fed synchronously with the circumferential speed of the photoconductive drum. The image transferred to the recording sheet at the transfer unit is fixed thereon by a fixing unit and then the recording paper is discharged out of the printer.
Although the photoconductive drum is rotatably supported by a unit frame with some play, a predetermined tolerance for engagement is necessary required between a rotary shaft of the photoconductive drum and the unit frame to enable the photoconductive drum to rotate. Thus a problem arises in that the rotary axis of the photoconductive drum is moved by the amount of the tolerance, and an image being formed is blurred by the movement due to the aforesaid resultant force. Note that the image is disturbed while the photoconductive drum is being moved by the resultant force, and is not disturbed when the photoconductive drum has been moved and then rotates at a given position.